Car electrical diagnostics
Tools and equipment
* Multimeter
* LED probe
* OBD-II scanner
* Diagnostic tool
*Car wiring diagram
Diagnostic procedure
1. Inspection
* Check the battery, terminals and wires for corrosion and loose connections.
* Inspect fuses and relays for burnt out or other damage.
* Check the wire connections for breaks or short circuits.
2. Multimeter testing
*Voltage check:
* Set the multimeter to DC Voltage (DCV) mode.
*Connect the red lead of the multimeter to the positive terminal of the battery and the black lead to the negative terminal.
* Voltage should be between 12-14 volts.
* Grounding check:
* Set the multimeter to resistance (ohms) mode.
*Connect the red lead of the multimeter to the positive terminal of the battery and the black lead to any point on the metal frame of the car.
* Resistance should be very low, close to zero.
3. Testing with LED probe
* Connect the probe to the positive terminal of the battery.
*Check the positive terminals of the fuses and relays to make sure they have power.
*Check the negative terminals of the fuses and relays to ensure they are grounded.
4. Diagnostics using an OBD-II scanner
* Connect the OBD-II scanner to the vehicle’s diagnostic connector.
*Run diagnostics and take note of any trouble codes.
* Look up trouble codes in the code reference book and determine possible causes.
5. Special diagnostics
* If standard diagnostic methods do not reveal the cause of the problem, more specialized diagnostics may be required.
* For example, you may need to use an oscilloscope to analyze electrical signals or test sensors and actuators using a diagnostic tool.
General Tips
*Safety First: Always disconnect the battery before performing diagnostics.
* Start with simple checks and gradually move on to more complex ones.
* Use the correct tools and follow the instructions for using them.
*Refer to your vehicle’s service manual for exact information on your specific electrical system.
*If you are unsure of your skills, it is recommended that you consult a qualified auto electrician.